Mental Math - Number Sense,ADD 10, SUB 10, ADD 100, SUB 100 Mental Math - Number SenseMental math refers to performing arithmetic calculations in your mind without using paper, a calculator, or other tools. Developing strong number sense helps with understanding numbers and their relationships, making it easier to solve problems quickly and efficiently. ADD 10Adding 10 to a number involves increasing the digit in the tens place by 1 while keeping the other digits the same. Example:25+10=3525 +